The present invention relates to universal joints, and more particularly to universal joints suitable for use in mooring devices.
Universal joints having high waterproofness are already known which include those disclosed in U.S. Pat. No. 4,206,717 and Examined Japanese Utility Model Publication No. 20898/82. These joints generally comprise a pair of yokes each having two trunnions projecting radially thereof, an annular intermediate ring having bearings arranged on two diametrical lines thereof intersecting each other at right angles for supporting the respective trunnions of the yokes, an annular projection having a spherical outer surface and formed on each of the yokes between the intermediate ring and a connecting flange at the outer end of the yoke, a pair of annular side covers each having an inner end fixed to the side edge portion of the intermediate ring and a spherical inner surface slidably in contact with the spherical outer surface of the annular projection, an annular seal member provided at the outer end of each side cover and in intimate contact with the spherical outer surface of the annular projection, and bearing holding closures closing bearing holes formed in the intermediate ring and fixed by setscrews to stepped portions of the intermediate ring around the holes, with a washer provided between the closure and the outer face of each trunnion. Each of the side covers comprises a pair of divided cover segments having connecting walls lapping over each other at their opposed ends and joined together with bolts and nuts.
With the universal joint described above, the side cover comprises two divided segments because the side cover, if in the form of an annular integral member, can not be passed over the connecting flange when the side cover is to be fixed to the intermediate ring after the pair of yokes and the intermediate ring are assembled, the outer end of the side cover, as well as its inner end, being diametrically much smaller than the connecting flange. If it is attempted to decrease the diameter of the connecting flange to avoid the interference of the flange with the annular side cover, the joint is unable to have any connecting portion. Accordingly, the annular side cover must invariably be divided into two segments, whereas the joint of the two cover segments is then likely to permit penetration of water therethrough. This problem is attributable to the structure that the spherical inner surface of the side cover is made slidable in contact with the spherical outer surface of the annular projection of the yoke. Furthermore, the weight of the universal joint itself acts on the setscews for fixing the holding closure and is therefore likely to cause damage to the bolts. Further to protect the sealed surface from corrosion, the yoke needs to be surface-treated as by building up or thermal spraying with SUS, but this procedure is cumbersome and results in a cost increase. When the universal joint is deformed in its entirety owing to a tensile axial force acting thereon, the side cover will be subjected to the force and is likely to break.